This invention relates to restarting electrodeless high intensity discharge (HID) lamps and more particularly, to a method and apparatus for shutting down electrodeless HID lamps so that they may be restarted instantaneously.
During normal operation of an electrodeless HID lamp, continuous microwave power is supplied to the lamp. Generally electrodeless discharge lamps are operated by a microwave field with a constant power level. Breakdown of the hot gas within the electrodeless discharge vessel is achieved by capacitively coupling high voltage pulses through the quartz wall. Under fixed microwave power and high voltage pulse conditions, the discharge will fail to restart during well defined intervals in the cooling phase even though gaseous breakdown occurs within the vessel.
Although high voltage pulses can in some circumstances, be used to restart electrodeless lamps there are problems associated with such methods. These problems include surface breakdown around the arc tube from the high voltage pulses and the safety concern of the high voltage source. The present invention discloses a method and apparatus for restarting hot electrodeless lamps without using high voltages.